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To use or not to use the Oxford comma (serial comma)? It depends. In Canada, don't use it. In the USA, use it. But it's not that simple.

The New York Times doesn't use it.

Curiously, Oxford University no longer uses it.

What is it?

Wikipedia explains, a serial comma or series comma (also called Oxford comma and Harvard comma) is a comma placed immediately before the coordinating conjunction (usually and, or, or nor)
in a series of three or more terms. For example, a list of three
countries might be punctuated either as "Portugal, Spain, and France"
(with the serial comma), or as "Portugal, Spain and France" (without the
serial comma)

Well illustrated in her book Eats, Shoots and Leaves, Lynn Truss of the BBC takes issue with poor punctuation.

I think a comma should be used for clarification. Advice is that one must be consistent and that the use or misuse of it makes editors go to arms.

Two fencers

JOKE: A panda walks into a restaurant, sits down and orders a sandwich. After
he finishes eating the sandwich, the panda pulls out a gun and shoots
the waiter, and then stands up to go. "Hey!" shouts the manager. "Where
are you going? You just shot my waiter and you didn't pay for your
sandwich!"

The panda yells back at the manager, "Hey man, I am a PANDA! Look it up!"

The
manager opens his dictionary and sees the following definition for
panda: "A tree-dwelling marsupial of Asian origin, characterised by
distinct black and white colouring. Eats shoots and leaves."

Oxford Comma Song by Vampire Weekend

What do you think about using an Oxford (serial) comma? I'm confused as hell.

Yes, I think it's best to use it but sometimes I'm not consistent, I confess. Of course, my present publisher does not use it so then I have no choice, but the Chicago Manual of Style says to use it, and many newspapers do. I'm confused about it, as we all are, but I think I will choose to use it for clarity.